Hitherto, a means for preventing the occurrences of damages, delustering, discoloring, etc., of paint films with floating matters or colliding matters, such as dusts, a rain, pebbles, etc., in the case of loading painted motorcars or the parts thereof, etc., on trucks or ships and transporting them to remote places, such as overseas places, etc., has been desired.
As such a preventive means, a means of coating a wax-series paint film material on the surfaces of the above-described articles or parts at a thickness of from 5 to 20 .mu.m has hitherto been known. However, there are problems such that it is difficult to form a wax paint film at a uniform thickness, whereby a uniform paint film is hard to obtain, the coated paint films are liable to be stained and are easily affected by a rain, a great deal of labor is required to apply the wax paint films and remove thereof, and the use of such wax paint films is liable to induce environmental problems such as the use of solvents, the treatment of waste liquids, etc.
On the other hand, to overcome the above-described problems by a sheet system, various surface protecting sheets of using a pressure-sensitive adhesive layer formed on a support for paint film adhesion are proposed. However, in the uses that the sheet is placed in the open air under high temperature for a long period of time as the case of the use for automobiles wherein the temperature of the roof portion of automobiles is said to reach 80.degree. C. when the automobiles are exposed outdoors in the summer season, there is a problem that it becomes difficult to peel the protecting sheet from a paint film by the deterioration of the strength, flexibility, etc., of the protecting sheet due to ultraviolet rays and the increase of the adhesive force of the protecting sheet with the passage of time.
In view of the above-described circumstance, it is proposed to overcome the problem of lowering the peelability of a protecting sheet after adhering for a long period of time by forming the pressure-sensitive adhesive layer of the protecting sheet with a high molecular weight polyisobutylene. However, in using such a pressure-sensitive layer, a paint film is liable to cause microdeformation with the increase of the molecular weight of the polymer and there is a difficulty that the protecting sheet thus proposed is unsatisfactory in the point of the compatibility of the prevention of the deformation of a paint film and the good peelability of the protecting sheet.
That is, the microdeformation described above means the deformation of a paint film by the adhesion of a protecting sheet and the occurrence of the microdeformation is particularly severe in a soft paint film. For example, in the case of using the protecting sheet for automobiles, when the automobiles are placed outdoors for a long period of time in the summer season, etc., a deformation such as a gap severely occurs in the paint film of the automobiles at the peripheral portion of the protecting sheet, the edges of entrapped air, etc., whereby the microdeformation occurs. The microdeformation is a defect of greatly reducing the commercial value of the automobiles according to the extent of peeling of the paint film, and the protecting sheet causing such a microdeformation is an article losing the fundamental efficiency and does not have a practical value.